The present invention relates to a floating-caliper spot-type disc brake provided with a brake disc rotating in the main direction of rotation and with a non-rotating brake carrier which is fastened to a vehicle on one side of the brake disc. The brake carrier partially extends over the edge of the brake disc and guides a brake caliper in an axially displaceable manner between guiding surfaces parallel to the brake disc's axis and supports the caliper in the circumferential direction of the brake disc, the brake caliper having connection with brake shoes arranged on both sides of the brake disc by means of its legs which are parallel with the brake disc, a first brake shoe of brake shoes being guided and held in the brake carrier on the side of the brake disc where the brake carrier is fastened.
Such a floating-caliper spot-type disc brake has come to knowledge in the German Patent DE-OS 2,048,519. The brake carrier projects beyond the brake disc by means of two arms running parallel with the brake disc axis and having projections on both sides of the brake disc, the projections facing each other and their front faces forming the guiding surfaces. The projections engage guiding grooves of the brake caliper, the bottom surfaces of which run parallel with the brake disc axis. There is a little play between the guiding surfaces and the bottom surfaces of the grooves as a result of which the brake caliper is easily displaceable in the axial direction. The brake shoe arranged on the side of the brake disc where the brake carrier is fastened can be applied to the brake disc by means of an actuating piston arranged in the adjacent leg of the brake caliper. The other brake shoe is positively fixed in the other leg of the brake caliper and is applied to the brake disc by the reaction force of the actuating piston which acts on the brake caliper.
When braking the rotating brake disc, at first the piston-side brake shoe, which is supported in the brake carrier, will abut the brake disc and will directly transmit all the ensuing frictional forces to the brake carrier. It is only then that the brake shoe, which is fixed in the leg of the brake caliper, will abut the brake disc, the ensuing frictional forces trying to displace the brake caliper in the main direction of rotation of the brake disc until it is able to support itself against the provided guiding surfaces of the brake carrier. Since the brake caliper on the brake carrier side of the disc, however, is in non-positive connection with the brake carrier due to the piston which is in frictional engagement with the brake shoe supported in the brake carrier, an inclination of the brake caliper and, hence, an uneven wear of the brake shoes will ensue since the plays due to the guidance between the brake caliper and the brake carrier will be overcome. Upon the release of the disc brake, the brake caliper will not return into its initial position and, upon a further braking operation, the inclination will become more and more pronounced until, due to abutment, the brake caliper will be supported between the guiding surfaces which, in relation to the brake disc, are respectively leading and trailing. This abutment defines the maximum inclination and, hence, the maximum of uneven wear of the brake shoes. A further inclination will now only be defined by the bending of the arm of the brake carrier which projects over the brake disc and which serves as a brake caliper support.